This invention relates to tape players used with dictating transcriber machines and, more particularly, to a back spacing apparatus for automatically rewinding a predetermined length of the tape when the tape player is switched from a playback mode over to a stop mode.
When typing speech information which has been recorded on a tape, it sometimes happens that some part of the reproduced speech is indistinct or cannot be caught. In such a case, it is necessary to hear again the indistinct part of the speech by stopping the tape, slightly rewinding it and then playing it back again. This means that the typist has to switch the tape deck to a rewind mode and then back to the playback mode again every time a word or phrase that cannot be clearly heard. This cumbersome operation is also necessary in such a case as when interrupting the typing due to an urgent task and subsequently resuming it.
In order to overcome the above inconvenience, back spacing apparatuses for automatically rewinding the tape are presently in use. Examples of such back spacing apparatus are disclosed in Japanese Patent Publication No. 11211/77 and Japanese Patent Disclosure No. 71304/75. However, although it is desirable that the tape is rewind for back spacing by a constant length, for instance a length corresponding to a couple of daily conversation words (i.e., 1 to 3 seconds), the prior-art back spacing apparatuses give no particular consideration to on the constant length automatic rewinding. More particularly, with the prior-art apparatus the rewinding operation is effected for a constant period of time, so that the rewound tape length varies with the diameter of the tape rolled on the supply reel side; it is large when the supply reel side tape roll diameter is large and is small when the diameter is small. This means that in case the rewound tape length is adjusted such that it is optimum when the supply reel side tape roll diameter is minimum, an unnecessarily large length of the tape is rewound when the tape roll diameter is maximum. Conversely, where adjustment is made such that the tape is rewound by an optimum length when the tape roll diameter is maximum, at the time when the tape roll diameter is small the rewound tape length is insufficient so that it is likely that a part of the repeated word or phrase cannot be heard.
In order to overcome this drawback, there have been proposed apparatuses with which the back spacing period, i.e., the rewound tape length, is manually variable, as disclosed in the afore-mentioned Japanese patent Publication No. 11211/77 and U.S. Pat. No. 3,758,726. However, the operation of manually changing the rewound tape length reduces the efficiency of the typist's work.